1. Field
One embodiment of the invention relates to an information processing apparatus such as a personal computer, and a power-saving control method which is applied to the information processing apparatus.
2. Description of the Related Art
In recent years, in information processing apparatuses such as personal computers, various kinds of buses, such as a PCI (Peripheral Component Interconnect) bus and an LPC (Low Pin Count) bus, have been used. In a certain kind of bus, not only signals which need to be supported as standard signals, but also some option signals which need to be supported only where necessary, are stipulated. For example, in the LPC bus standard, a power-down signal is stipulated as one of option signals. The power-down signal is a signal which is used in order to instruct a peripheral device on the LPC bus to prepare for power-off. For example, a peripheral device, which needs to execute a predetermined process prior to power-off, requires the input of the power-down signal.
In usual cases, the LPC bus is used for interconnection between a controller (chipset) and peripheral devices. However, in the current situation, only limited types of controllers have the function of outputting an option signal such as a power-down signal, and there are many types of controllers which do not support the output of the power-down signal.
In the system configuration using a controller which does not support the output of a power-down signal, it is difficult to normally operate the function of a peripheral device which requires the input of a power-down signal. Thus, in a computer including a controller which does not support the output of a power-down signal, it is necessary to treat the peripheral device which requires the input of a power-down signal as a non-supported device.
Jpn. Pat. Appln. KOKAI Publication No. 2002-236529 discloses a system for executing power-saving control for a graphics controller which does not have a pin for power-saving control. In this system, the system BIOS directly accesses an I/O register of a graphics controller, and controls the operation of hardware components in the graphics controller.
In this system, however, no consideration is given to the scheme for supporting a peripheral device which requires the input of an option signal such as a power-down signal.
In order to enabling the system configuration, which uses a controller that does not support the output of a power-down signal, to support a peripheral device which requires the input of a power-down signal, it is necessary to realize a novel function for controlling the generation timing of a power-down signal without using the controller.